Question Number: 169
PDR Number: SQ22-000538
Date Submitted: 21/11/2022
Department or Body: Department of Health
Question 49 Both Therapeutic Goods Administration (TGA) provisionally approved Pfizer (COMIRNATY), and Moderna (SPIKEVAX) vaccines consist of N1-methyl-pseudouridine(Ψ) modified (N1- methyl-Ψ) mRNA encoding the SARS-COVID-19 spike protein. N1-methylpseudouridine is a naturally occurring modified nucleotide, that is highly abundant and naturally widespread in cells and its use does not change the features of the mRNA. Pseudouridine or N1-Methyl-Pseudouridine has been used in the development of mRNA therapeutics, including mRNA vaccines, for many years with an aim to enhance RNA stability, antigen expression and adaptive immune responses, and to reduce cytotoxicity of modified mRNA, available at:(https://pubmed.ncbi.nlm.nih.gov/30135514/, https://pubmed.ncbi.nlm.nih.gov/28251988/, https://pubmed.ncbi.nlm.nih.gov/34805188/ and https://pubmed.ncbi.nlm.nih.gov/34075344/). For identical reasons, N1-Methyl-Pseudouridine was used in the Pfizer (COMIRNATY) and Moderna (SPIKEVAX) mRNA vaccines to ensure translation efficiency, stability and safety of the mRNA vaccines. It has also been reported that N1-Methyl-Pseudouridine modified mRNA exhibits higher efficacy (more than 90% of efficacy against COVID-19 symptoms) as compared to the unmodified mRNA vaccines (lower than 50%) encoding the SARS-COVID-19 spike protein (available at: https://pubmed.ncbi.nlm.nih.gov/34145413/). To minimise any misreading risks associated with stop signals (ΨGAΨGA in Pfizer/BioNTech’s vaccine, and ΨGAΨAAΨAG in the Moderna’s vaccine), both mRNA vaccines use consecutive stop codons as a fail-safe mechanism, so that no frameshifting occurs if the first stop codon fails (available at: https://pubmed.ncbi.nlm.nih.gov/34805188/). Based on the knowledge and experience from decades of research and trials with mRNA therapeutics, the COVID-19 vaccine manufacturers were able to design an appropriate dosing regimen and threshold of doses ensuring the proper balance between immune responses and safety of these vaccines. Animal toxicology studies of the Pfizer and Moderna mRNA vaccines at doses 200-times higher than the human dose on a dose/body weight basis have not shown any safety concerns. Question 50 See response to Question 49.